HOST SPECIES PREFERENCE AND LARVAL PERFORMANCE IN THE WOOD-BORING BEETLE PHORACANTHA-SEMIPUNCTATA F

Adults of the wood-boring beetle Phoracantha semipunctata F. showed variability in their attractiveness to five varieties of Eucalyptus when presented with an array of logs in a natural setting. Logs of two host varieties (E. camaldulensis Dehnhardt and the hybrid E. trabutii) attracted two to three times more adult beetles than did logs of other host species (E. cladocalyx F., E. grandis Hill ex Maiden and E. tereticornis Small). In the field, high oviposition rates by P. semipunctata adults resulted in severe competition among larvae. Larval survivorship was low in field logs of E. trabutii and high in E. cladocalyx logs, although these hosts were the most and least attractive to the adult beetles, respectively. However, when logs were hand infested at low larval densities, survivorship of P. semipunctata larvae was highest in logs of both E. camaldulensis and E. trabutii. These findings suggest that adult beetles in the field were most attracted to those logs of Eucalyptus species that represented the highest quality hosts for their progeny under conditions of reduced larval competition.